Message-ID: <5633BD2D.1050808@broadcom.com>
Date:	Fri, 30 Oct 2015 11:55:41 -0700
From:	Ray Jui <rjui@...adcom.com>
To:	Brian Norris <computersforpeace@...il.com>
CC:	Anup Patel <anup.patel@...adcom.com>,
	David Woodhouse <dwmw2@...radead.org>,
	Linux MTD <linux-mtd@...ts.infradead.org>,
	Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Catalin Marinas <catalin.marinas@....com>,
	"Will Deacon" <will.deacon@....com>,
	Sudeep Holla <sudeep.holla@....com>,
	"Ian Campbell" <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	Scott Branden <sbranden@...adcom.com>,
	Florian Fainelli <f.fainelli@...il.com>,
	Pramod Kumar <pramodku@...adcom.com>,
	Vikram Prakash <vikramp@...adcom.com>,
	Sandeep Tripathy <tripathy@...adcom.com>,
	"Linux ARM Kernel" <linux-arm-kernel@...ts.infradead.org>,
	Device Tree <devicetree@...r.kernel.org>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	bcm-kernel-feedback-list <bcm-kernel-feedback-list@...adcom.com>
Subject: Re: [PATCH v3 2/2] arm64: dts: Add BRCM IPROC NAND DT node for NS2



On 10/30/2015 11:49 AM, Brian Norris wrote:
> On Wed, Oct 28, 2015 at 09:08:02AM -0700, Ray Jui wrote:
>> On 10/28/2015 2:06 AM, Anup Patel wrote:
>>>
>>> I think for a newly created OF devices the Linux device driver framework will
>>> match the platform drivers in the order in which they are registered by module
>>> init functions. Now the order of module init function calls will be based how
>>> the .initcall section is formed by linker and order in which objects are linked.
>>>
>>
>> Yes, what you said is my understanding as well, but then here is the
>> mystery. This is the link order in brcmnand/Makefile:
>>
>> 1 # link order matters; don't link the more generic brcmstb_nand.o
>> before the
>> 2 # more specific iproc_nand.o, for instance
>> 3 obj-$(CONFIG_MTD_NAND_BRCMNAND) += iproc_nand.o
>> 4 obj-$(CONFIG_MTD_NAND_BRCMNAND) += bcm63138_nand.o
>> 5 obj-$(CONFIG_MTD_NAND_BRCMNAND) += brcmstb_nand.o
>> 6 obj-$(CONFIG_MTD_NAND_BRCMNAND) += brcmnand.o
>>
>> Based on the order above, probe from iproc_nand should always be
>> called first if a matching compatible string is found. If so, then
>> why having both compatible strings "brcm,brcmnand" and
>> "brcm,nand-iproc" causes issues for NS2 (I remember it broke
>> smoketest in the past when you submitted the change)? I'm not saying
>> we should have "brcm,brcmnand" for iProc devices, but I don't get
>> why it would cause any issue.
>
> FWIW, the above hack doesn't do anything if these are built as modules,
> AFAICT. So I guess udev's (or similar) module rules would be another
> point of failure here? Not that any of us probably care too much about
> this driver as a module, but just throwing it out there...
>
> I have a feeling we'll have to solve this locally, by avoiding having
> "independent" drivers handling similar compatible properties, as I
> expect (despite our expectation that compatible ordering should matter)
> this problem will not be solved any time soon in the generic
> infrastructure.
>
> Or we can just use a hack (as Anup is doing) to leave off the
> "brcm,brcmnand" compatibility property. Unless someone has brilliant
> ideas, I guess we go with Anup's hack for now.

I'm fine with that, :)

Ray

>
> Brian
>
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